Inferring positional behavior on the basis of osteometric characters: a model for the fossil taxon Epipliopithecus vindobonensis

This study examines whether osteometric traits of the shoulder and elbow can be used to infer the positional behavior of extant and fossil taxa. Seven extant taxa for which there are published data on positional behavior (Hylobates concolor, Ateles geofrroyi, Brachytles arachnoides, Lagothrix lagothricha, Pygathrix nemaeus, Cebus apella, and Alouatta seniculus), and one fossil taxon, Epipliopithecus vindobonensis were selected for analysis. The extant sample was selected as these species engage in a wide range of positional behaviors. Thirty-eight osteometric characters of the shoulder and elbow were measured on each species and compared using Principal Component Analysis (PCA). The PCA identified several anatomical traits that are associated with specific types of positional behavior. It was possible therefore, to compare the shoulder and elbow anatomy of Epipliopithecus vindobonensis to the anatomy of these extant taxa in order to infer its positional behavior. The humerus of Epipliopithecus has a variety of features that are found in Cebus, Alouatta, Lagothrix and Ateles, but none of the extant taxa has the whole suite of features found in the fossil species. The results indicate that Eplipliopithecus is most closely associated with Lagothrix, and that Eplipliopithecus, like Lagothrix, engaged in quadrupedalism and suspensory behaviors.